Membership is device-specific and is attached to your Google Play or App Store account. If you purchase a subscription, it will be applied to any/all of your profiles (e.g. if you have both a solo & partner profile, the purchased subscription will be applied to both profiles). Your partner would need to purchase their own subscription to receive membership benefits on their own device.
Note: if you and your partner share GooglePlay or App Store accounts, errors can occur causing the purchase to be applied to the incorrect account. Please ensure you are purchasing with your own account to avoid this issue.